1. Field of the Invention
The present invention relates to an exposure mask which is used, for example, when an etching pattern of an air bearing surface (ABS) is exposed to the surface of a resist layer formed on the surface, that is opposed to a recording medium, of a substrate such as a slider bar, and more particularly, the invention relates to an exposure mask capable of securely aligning itself with the slider bar and to an exposure method using the exposure mask.
2. Description of the Related Art
A magnetic head device mounted on a hard disk drive or the like includes a slider provided on the tip of gimbals composed of a spring material, and on the edge of the slider, a thin film element for recording and reproducing is deposited.
The slider has a flying surface, i.e., a so-called xe2x80x9cABSxe2x80x9d, which is opposed to the recording medium, and the slider flies above the recording medium by means of air that flows over the surface of the recording medium. While the slider is flying over the recording medium, recording or reproducing is performed on the recording medium by the thin film element provided on the slider.
In order to fabricate the slider, first, a circular ceramic material is formed, and a plurality of thin film elements are formed in parallel on the ceramic material by sputtering. The ceramic material is then sliced to produce a plurality of slender slider bars.
Next, a plurality of slider bars 20 are arrayed in parallel so that surfaces 21 that are opposed to a recording medium are aligned as shown in FIG. 5, and the slider bars 20 are retained by a jig or the like.
As shown in FIG. 5, a plurality of thin film elements 22 appear on the surface 21 of the slider bar 20.
A photosensitive resist layer (not shown on the drawing) is formed on the surface 21.
Next, a plurality of etching patterns of an ABS are exposed onto the surface of the resist layer by using an exposure mask.
FIGS. 6 and 7 show steps in an exposure method using a conventional exposure mask.
First, an exposure mask 23 shown in FIG. 6 is aligned with a slider bar 20 that is disposed on the uppermost or lowermost side shown in FIG. 5.
The exposure mask 23 has a plurality of light transmission sections 24 having the same shape as that of the ABS pattern, and a window 26 having alignment keys (marks) 25 and 25 is provided at least between two light transmission sections 24 and 24.
The exposure mask 23 shown in FIG. 6 is provided with, for example, three light transmission sections 24 and one window 26.
As shown in FIG. 6, a region (diagonally shaded in the drawing) excluding the light transmission sections 24 and the window 26 is deposited with, for example, chromium (Cr) so as not to transmit light. The alignment keys 25 are also composed of a Cr film.
As shown in FIG. 6, the exposure mask 23 is moved up and down from side to side so that the thin film element 22 formed on the slider bar 20 is positioned in the center between the two alignment keys 25 and 25 formed in the window 26 of the exposure mask 23.
After the thin film element 22 is positioned in the center between the alignment keys 25 and 25, the exposure mask 23 is slid to the left by a predetermined distance as shown in FIG. 7.
By sliding the exposure mask 23 to the left, the thin film element 22 is aligned at a predetermined position within the light transmission section 24 formed on the exposure mask 23.
After the slider bar 20 and the light transmission sections 24 of the exposure mask 23 are aligned as described above, the photosensitive resist layer formed on the slider bar 20 is exposed through the light transmission sections 24.
Furthermore, the exposure mask 23 is slid to the left and upward or downward in the drawing and on the unexposed surface 21 of the slider bar 20, the thin film element 22 of the slider bar 20 and the light transmission section 24 of the exposure mask 23 are aligned as described with reference to FIGS. 6 and 7, and then, the photosensitive resist layer formed on the slider bar 20 is exposed.
In this way, a plurality of etching patterns of the ABS are exposed onto the resist layer formed on the surface 21 of all the slider bars 20 shown in FIG. 5.
Since the photosensitive resist layer is of a negative type, the exposed resist layer remains on the surface 21 of the slider bar 20 in the development process and the unexposed resist layer is removed by a developer.
In FIG. 7, the resist layer on the slider bar 20 corresponding to the light transmission sections 24 is left in the same shape as that of the light transmission sections 24 by exposure and the resist layer other than the above is removed.
Although the resist layer on the slider bar 20 corresponding to the window 26 shown in FIG. 7 is also left by exposure, since the slider bar 20 in this section is finally cut along lines A and B shown in FIG. 7 and removed, the shape of the window 26 will not remain on finished sliders.
After exposure and development, a dry etching step is carried out. Then, the slider bar 20 is cut along the lines A and B in FIG. 7 to obtain a plurality of sliders.
The exposure mask 23 shown in FIG. 6, however, gives rise to the following problems.
The alignment keys 25 and 25 formed in the window 26 of the exposure mask 23 are provided only for aligning the light transmission section 24 of the exposure mask 23 and the thin film element 22 of the slider bar 20, and therefore, the shape of the window 26 must not be left by the exposure and development process on finished sliders.
Consequently, as shown in FIGS. 6 and 7, the window 26 is formed between the light transmission sections 24 and 24, and finally, a portion of the slider bar 20 corresponding to the window 26 is removed by being cut along the cutoff lines A and B (refer to FIG. 7).
However a space between the cutoff lines A and B shown in FIG. 7 is very small, and in particular, since sliders are miniaturized as the recording density increases, the space between the cutoff lines A and B is required to be narrowed as much as possible so that the portion of slider bar 20 to be removed is minimized.
Therefore, as the space between the cutoff lines A and B is narrowed, the size of the window 26 in the exposure mask 23 must be decreased. If the window 26 is made smaller, when the exposure mask 23 is slid up and down to align the exposure mask 23 with the slider bar 20, the thin film element 22 fails to be fitted into the window 26, resulting in decrease in alignment accuracy (alignment accuracy of the exposure mask).
Furthermore, when a plurality of slider bars 20 are arrayed in parallel as shown in FIG. 5, etching patterns of the ABS are formed on the slider bar 20 in the exposure step as shown in FIGS. 6 and 7, and then, the exposure mask is slid upward or downward in the drawing to perform the exposure step onto an unexposed slider bar 20.
However, as shown in FIG. 5, there is a possibility that a thin film element 22A on a slider bar 20 disposed uppermost and a thin film element 22B on a slider bar 20 disposed under the above slider bar 20 are not properly arranged in the longitudinal direction in the drawing, and even if the exposure mask 23 is slid downward in the drawing with the thin film element 22A being aligned with the alignment keys 25 and 25 in the window 26 of the exposure mask 23 shown in FIG. 6, the thin film element 22B is not fitted into the window 26 of the exposure mask 23.
Thus, if the thin film element 22B does not appear in the window 26, there is difficulty in determining the correct direction in which the exposure mask 23 is moved, and thus the alignment with the slider bar 20 cannot be performed properly, resulting in decrease in operating efficiency and alignment accuracy.
In order to increase the operating efficiency and the like by using the exposure mask 23 shown in FIGS. 6 and 7, the positional accuracy of the thin film elements 22 formed on the individual slider bars 20 must be increased.
The present invention overcomes the difficulties noted above with respect to the related art. It is an object of the present invention to provide an exposure mask in which operating efficiency and alignment accuracy can be improved even if sliders are miniaturized and to provide an exposure method using the exposure mask.
In one aspect, in accordance with the present invention, an exposure mask, which is used for exposing a photosensitive resist layer formed on the surface of a substrate having a thin film element on the surface region so that the resist layer is left in the shape of an ABS pattern, includes a mark provided within a light transmission section for determining a relative position between the substrate and the light transmission section on the basis of the thin film element.
In the present invention, preferably, the photosensitive resist layer is of a negative type and the mark is provided within the light transmission section having the shape of the ABS pattern. Alternatively, preferably, the photosensitive resist layer is of a positive type and the mark is provided within the light transmission section excluding a section having the shape of the ABS pattern.
In the present invention, the mark may be provided at a position being shifted by a predetermined distance from the position in which the thin film element is to be placed relative to the exposure mask.
In another aspect, in accordance with the present invention, an exposure method using the exposure mask includes the steps of:
determining a relative position between the substrate and the light transmission section on the basis of the thin film element by the mark provided within the light transmission section of the exposure mask;
exposing the photosensitive resist layer on the surface of the substrate through the light transmission section of the exposure mask; and
developing the exposed photosensitive resist layer so that the resist layer is left in the shape of the ABS pattern.
In the present invention, a relative position between the substrate and the light transmission section may be determined by aligning the mark with the thin film element and then by shifting the exposure mask by a predetermined distance.
Conventionally, an exposure mask used in the exposure process has a shape as shown in FIG. 6. Between light transmission sections 24 and 24 having the shape of an ABS pattern, a window 26 is formed having alignment keys (marks) 25 and 25 for aligning the light transmission section 24 of an exposure mask 23 with a thin film element 22 of a slider bar 20.
However, a space between the light transmission sections 24 and 24 is so small that the size of the window 26 cannot be greatly increased. Consequently, even if the exposure mask 23 is moved in order to align the alignment keys 25 in the window 26 with the thin film element 22 of the slider bar 20, the thin film element 22 may not appear in the window 26 formed on the exposure mask 23. When the thin film element 22 does not appear in the window 26 as described above, the exposure mask 23 cannot be properly aligned with the slider bar 20.
Accordingly, in the present invention, in order to form the alignment keys in the largest possible area, the alignment keys are formed within the light transmission section which is required for forming the ABS pattern.
Exposure masks shown in FIGS. 2 and 4 are embodiments of the present invention.
For example, an exposure mask 4 shown in FIG. 2 has two alignment keys 6 and 6 within a light transmission section 5A having the same shape as that of an ABS pattern.
The spot in the light transmission section 5A in which the alignment keys 6 and 6 are formed corresponds to a rail portion of the ABS, and the area thereof is very large.
Therefore, if the alignment keys 6 are formed within the light transmission section 5A, when a plurality of slider bars 1 are arrayed in parallel as shown in FIG. 1 and, for example, by moving an exposure mask 4 shown in FIG. 2 in the vertical direction in the drawing, the exposure mask 4 is transferred from a slider bar 1 to the adjacent slider bar 1, it is highly possible that the thin film element 3 of the adjacent slider bar 1 appears within the light transmission section 5A of the exposure mask 4, and the thin film element 3 can be properly aligned with the alignment keys formed in the light transmission section 5A.